Arrange potato nuggets in a single layer on a baking sheet.
Bake potato nuggets in the preheated oven until golden and heated through, 24 to 26 minutes.
Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease. Stir water and taco seasoning mix into beef; cook and stir until liquid is thickened, 2 to 3 minutes.
Pour cheese sauce into a microwave-safe bowl; heat in the microwave for 30 seconds, stir. Continue heating in 15-second intervals until hot, stirring between intervals.
Spread potato nuggets on a serving plate. Top with meat, cheese sauce, sour cream, onion, and jalapeno slices.