Games like The Powder Toy
Games like The Powder Toy include People Playground, Kerbal Space Program, Garry's Mod, BeamNG.drive, and Besiege. We matched them by the tags players give The Powder Toy on Steam (Simulation, Sandbox, 2D, Pixel Graphics, and Physics): closest matches first, and among equally close ones the better-known games.

People Playground
Shared: Sandbox · Physics · 2D

Kerbal Space Program
Shared: Simulation · Sandbox · Physics

Garry's Mod
Shared: Sandbox · Physics · Moddable

BeamNG.drive
Shared: Simulation · Physics · Sandbox

Besiege
Shared: Simulation · Sandbox · Physics

Space Engineers
Shared: Sandbox · Simulation · Physics

Cities: Skylines
Shared: Simulation · Sandbox · Singleplayer

Universe Sandbox
Shared: Simulation · Sandbox · Physics

Totally Accurate Battle Simulator
Shared: Simulation · Sandbox · Physics

Sand:box
Shared: Simulation · Sandbox · 2D

Terraria
Shared: Sandbox · 2D · Pixel Graphics

Car Mechanic Simulator 2018
Shared: Simulation · Singleplayer · Sandbox

Spaceflight Simulator
Shared: Sandbox · Simulation · 2D

Brick Rigs
Shared: Sandbox · Destruction · Simulation

Stardew Valley
Shared: Pixel Graphics · Simulation · Sandbox

Cities: Skylines II
Shared: Simulation · Sandbox · Singleplayer

Graveyard Keeper
Shared: Simulation · Pixel Graphics · Sandbox

Teardown
Shared: Sandbox · Physics · Destruction

Space Engineers 2
Shared: Sandbox · Simulation · Physics

WorldBox - God Simulator
Shared: Sandbox · Simulation · Pixel Graphics

Kerbal Space Program 2
Shared: Sandbox · Simulation · Physics

Prison Architect
Shared: Simulation · Sandbox · 2D

Noita
Shared: Physics · Pixel Graphics · Sandbox

The Sims™ 4
Shared: Simulation · Sandbox · Singleplayer