David Njoku helped the Browns clinch a playoff berth on the field on Thursday night ... and then he helped Cleveland's fans celebrate off of it -- shooting booze with Dawg Pound supporters in a parking lot!!!
The star tight end was seen performing the awesome gesture just minutes after Cleveland's 37-20 victory over the Jets.
In video from the scene, you can see Njoku -- who had 134 receiving yards in the "TNF" victory -- grab a shot glass, surround himself with fans and give a little toast before he throws the drink back.