diff --git a/drake_bazel_download/README.md b/drake_bazel_download/README.md
index eca70de5..333396fc 100644
--- a/drake_bazel_download/README.md
+++ b/drake_bazel_download/README.md
@@ -8,17 +8,18 @@ For an introduction to Bazel, refer to
 
 ## Instructions
 
-First, run the `install_prereqs` script to download the Drake source to `/opt/drake/`.
-This also runs Drake's setup script to install the required Ubuntu packages:
+First, run the `install_prereqs` script to download the
+Drake source to `/opt/drake/`. This also runs Drake's
+setup script to install the required Ubuntu packages:
 
 ```bash
-sudo setup/install_prereqs
+setup/install_prereqs
 ```
 
 Additionally, if you don't already have bazel or bazelisk installed, then install bazelisk:
 
 ```bash
-sudo setup/install_bazelisk
+setup/install_bazelisk
 ```
 
 Then, to build and test all apps:
diff --git a/drake_bazel_download/setup/install_bazelisk b/drake_bazel_download/setup/install_bazelisk
index 0032a5a6..f7be3525 100755
--- a/drake_bazel_download/setup/install_bazelisk
+++ b/drake_bazel_download/setup/install_bazelisk
@@ -6,12 +6,12 @@
 
 set -euxo pipefail
 
-if [[ "${EUID:-}" -ne 0 ]]; then
-  echo 'This script must be run as root' >&2
-  exit 2
+maybe_sudo=
+if [[ "${EUID}" -ne 0 ]]; then
+  maybe_sudo=sudo
 fi
 
 wget -O bazelisk.deb \
   https://github.com/bazelbuild/bazelisk/releases/download/v1.24.0/bazelisk-amd64.deb
-dpkg -i bazelisk.deb
+${maybe_sudo} dpkg -i bazelisk.deb
 rm -f bazelisk.deb
diff --git a/drake_bazel_download/setup/install_prereqs b/drake_bazel_download/setup/install_prereqs
index 42113566..f49b09af 100755
--- a/drake_bazel_download/setup/install_prereqs
+++ b/drake_bazel_download/setup/install_prereqs
@@ -31,20 +31,20 @@
 
 set -euxo pipefail
 
-if [[ "${EUID:-}" -ne 0 ]]; then
-  echo 'This script must be run as root' >&2
-  exit 2
+maybe_sudo=
+if [[ "${EUID}" -ne 0 ]]; then
+  maybe_sudo=sudo
 fi
 
-apt-get update
-apt-get install --no-install-recommends lsb-release
+${maybe_sudo} apt-get update
+${maybe_sudo} apt-get install --no-install-recommends lsb-release
 
 if [[ "$(lsb_release -sc)" != 'jammy' ]]; then
   echo 'This script requires Ubuntu 22.04 (Jammy)' >&2
   exit 3
 fi
 
-apt-get install --no-install-recommends $(cat <<EOF
+${maybe_sudo} apt-get install --no-install-recommends $(cat <<EOF
   ca-certificates
   wget
 EOF
@@ -58,4 +58,4 @@ tar -xf drake.tar.gz -C /opt
 # Show version for debugging; use echo for newline / readability.
 echo -e "\ndrake VERSION.TXT: $(cat /opt/drake/share/doc/drake/VERSION.TXT)\n"
 
-/opt/drake/share/drake/setup/install_prereqs
+${maybe_sudo} /opt/drake/share/drake/setup/install_prereqs
diff --git a/drake_bazel_external/README.md b/drake_bazel_external/README.md
index 173b2d6b..d471eb59 100644
--- a/drake_bazel_external/README.md
+++ b/drake_bazel_external/README.md
@@ -7,9 +7,9 @@ For an introduction to Bazel, refer to
 
 ## Instructions
 
-First, run the `install_prereqs` script to download the Drake source to `drake-master/`
-(from the current directory). This also runs Drake's setup script to
-install the required Ubuntu packages:
+First, run the `install_prereqs` script to download
+the Drake source to `drake-master/` (from the current directory).
+This also runs Drake's setup script to install the required Ubuntu packages:
 
 ```bash
 setup/install_prereqs
diff --git a/drake_bazel_external/setup/install_prereqs b/drake_bazel_external/setup/install_prereqs
index f30b1f83..a967c81e 100755
--- a/drake_bazel_external/setup/install_prereqs
+++ b/drake_bazel_external/setup/install_prereqs
@@ -4,7 +4,12 @@
 
 set -euxo pipefail
 
-sudo apt-get install --no-install-recommends $(cat <<EOF
+maybe_sudo=
+if [[ "${EUID}" -ne 0 ]]; then
+  maybe_sudo=sudo
+fi
+
+${maybe_sudo} apt-get install --no-install-recommends $(cat <<EOF
   wget
 EOF
 )
@@ -18,4 +23,4 @@ trap 'rm -f drake.tar.gz' EXIT
 tar -xf drake.tar.gz
 
 # Install the source prereqs
-sudo drake-master/setup/ubuntu/install_prereqs.sh
+${maybe_sudo} drake-master/setup/ubuntu/install_prereqs.sh
diff --git a/drake_bazel_external_legacy/README.md b/drake_bazel_external_legacy/README.md
index 262d19ad..ad42f2d8 100644
--- a/drake_bazel_external_legacy/README.md
+++ b/drake_bazel_external_legacy/README.md
@@ -12,9 +12,9 @@ For an introduction to Bazel, refer to
 
 ## Instructions
 
-First, run the `install_prereqs` script to download the Drake source to `drake-master/`
-(from the current directory). This also runs Drake's setup script to
-install the required Ubuntu packages:
+First, run the `install_prereqs` script to download the
+Drake source to `drake-master/` (from the current directory).
+This also runs Drake's setup script to install the required Ubuntu packages:
 
 ```bash
 setup/install_prereqs
diff --git a/drake_bazel_external_legacy/setup/install_prereqs b/drake_bazel_external_legacy/setup/install_prereqs
index f30b1f83..a967c81e 100755
--- a/drake_bazel_external_legacy/setup/install_prereqs
+++ b/drake_bazel_external_legacy/setup/install_prereqs
@@ -4,7 +4,12 @@
 
 set -euxo pipefail
 
-sudo apt-get install --no-install-recommends $(cat <<EOF
+maybe_sudo=
+if [[ "${EUID}" -ne 0 ]]; then
+  maybe_sudo=sudo
+fi
+
+${maybe_sudo} apt-get install --no-install-recommends $(cat <<EOF
   wget
 EOF
 )
@@ -18,4 +23,4 @@ trap 'rm -f drake.tar.gz' EXIT
 tar -xf drake.tar.gz
 
 # Install the source prereqs
-sudo drake-master/setup/ubuntu/install_prereqs.sh
+${maybe_sudo} drake-master/setup/ubuntu/install_prereqs.sh
diff --git a/drake_cmake_external/README.md b/drake_cmake_external/README.md
index aa9bb056..ad0aedd9 100644
--- a/drake_cmake_external/README.md
+++ b/drake_cmake_external/README.md
@@ -4,9 +4,9 @@ This pulls in Drake using the CMake `ExternalProject_Add(drake)` mechanism.
 
 ## Instructions
 
-First, run the `install_prereqs` script to download the Drake source to `drake-master/`
-(from the current directory). This also runs Drake's setup script to
-install the required Ubuntu packages:
+First, run the `install_prereqs` script to download the
+Drake source to `drake-master/` (from the current directory).
+This also runs Drake's setup script to install the required Ubuntu packages:
 
 ```bash
 setup/install_prereqs
diff --git a/drake_cmake_external/setup/install_prereqs b/drake_cmake_external/setup/install_prereqs
index f30b1f83..a967c81e 100755
--- a/drake_cmake_external/setup/install_prereqs
+++ b/drake_cmake_external/setup/install_prereqs
@@ -4,7 +4,12 @@
 
 set -euxo pipefail
 
-sudo apt-get install --no-install-recommends $(cat <<EOF
+maybe_sudo=
+if [[ "${EUID}" -ne 0 ]]; then
+  maybe_sudo=sudo
+fi
+
+${maybe_sudo} apt-get install --no-install-recommends $(cat <<EOF
   wget
 EOF
 )
@@ -18,4 +23,4 @@ trap 'rm -f drake.tar.gz' EXIT
 tar -xf drake.tar.gz
 
 # Install the source prereqs
-sudo drake-master/setup/ubuntu/install_prereqs.sh
+${maybe_sudo} drake-master/setup/ubuntu/install_prereqs.sh
diff --git a/drake_cmake_installed/README.md b/drake_cmake_installed/README.md
index 54e65b8a..fb96e8b0 100644
--- a/drake_cmake_installed/README.md
+++ b/drake_cmake_installed/README.md
@@ -13,7 +13,7 @@ These instructions are only supported for Ubuntu 22.04 (Jammy).
 
 # Download Drake source to /opt/drake/ and install
 # various system dependencies
-sudo setup/install_prereqs
+setup/install_prereqs
 
 ###############################################################
 # Install Drake to $HOME/drake
diff --git a/drake_cmake_installed/setup/install_prereqs b/drake_cmake_installed/setup/install_prereqs
index 3f64e06c..82dd914b 100755
--- a/drake_cmake_installed/setup/install_prereqs
+++ b/drake_cmake_installed/setup/install_prereqs
@@ -54,20 +54,20 @@ case "$OSTYPE" in
 
     linux*)
     # Ubuntu specific installations
-    if [[ "${EUID:-}" -ne 0 ]]; then
-      echo 'This script must be run as root' >&2
-      exit 2
+    maybe_sudo=
+    if [[ "${EUID}" -ne 0 ]]; then
+      maybe_sudo=sudo
     fi
 
-    apt-get update
-    apt-get install --no-install-recommends lsb-release
+    ${maybe_sudo} apt-get update
+    ${maybe_sudo} apt-get install --no-install-recommends lsb-release
 
     if [[ "$(lsb_release -sc)" != 'jammy' ]]; then
       echo 'This script requires Ubuntu 22.04 (Jammy)' >&2
       exit 3
     fi
 
-    apt-get install --no-install-recommends $(cat <<EOF
+    ${maybe_sudo} apt-get install --no-install-recommends $(cat <<EOF
       ca-certificates
       wget
 EOF
@@ -78,8 +78,8 @@ EOF
     trap 'rm -f drake.tar.gz' EXIT
     tar -xf drake.tar.gz -C /opt
 
-    apt-get update
-    apt-get install --no-install-recommends $(cat <<EOF
+    ${maybe_sudo} apt-get update
+    ${maybe_sudo} apt-get install --no-install-recommends $(cat <<EOF
       python3-all-dev
 EOF
     )