Somerset 223 for 6 (Trego 94) beat Sussex 221 (Jones 5-33) by four wickets
Chasing a target of 22, Peter Trego and Chris Gazzard got Somerset off to a strong start in a first-wicket stand of 130, and then Trego and Suppiah took the score to 181 before the innings lost direction.
Trego started the rot when he holed out to long-on looking to reach his hundred with a six and then Gazzard chipped a return catch to offspinner Ollie Rayner - five wickets went for 22, but Omari Banks and Ben Phillips clubbed Somerset to victory with 14 balls to spare.
Sussex also had their lower order to thank for bailing them out of trouble after Steffan Jones blew away their top order with a four-wicket spell to leave them 48 for 5. Rory Hamilton-Brown and Ben Brown started the recovery with a sixth-wicket stand of 74, and when both fell in quick succession Ollie Rayner and Tom Smith also put on 74 for the eighth wicket. Jones returned to polish off the tail and finish with 5 for 33.