Liverpool legend Fowler, 31, is edging closer to full fitness after a thigh injury and should earn at least a place on the bench.
Hasselbaink, meanwhile, proved he is fit and ready for action after making a goalscoring start to his Bluebirds career last Tuesday. The former Leeds, Chelsea and Middlesbrough forward, 35, claimed a brace in Cardiff's 4-2 win at Hereford in a behind-closed-doors friendly.
Neither player featured in Saturday's home defeat against Coventry, but Jones confirmed they will make their bows against Orient.
Jones said: "They were not quite ready for Saturday's game but they will get a run-out on Tuesday."
The pair's availability leaves former Aston Villa midfielder Ricky Scimeca as the only injury absentee.
Meanwhile, Orient boss Martin Ling will name an unchanged side for the tie.
The O's maintained their 100 per cent start to the season with a 2-0 win at Crewe on Saturday, leaving Ling's men top of the League One table and in confident mood ahead of the trip to Wales.
Orient boss Ling is likely to call on Paul Terry to fill in again at right-back as captain Stephen Purches continues his recovery from the hamstring injury that ruled him out of Saturday's victory, while Anton Thelwell will continue to captain the side in his absence.
Former Luton striker Adam Boyd will be hoping to maintain his hot streak in front of goal after netting again in the win at Crewe, his third goal since his summer move to Brisbane Road.