These are the best Prime Day deals under $100, from smartwatches to LifeStraws. Be sure to check out our full list of the Best Prime Day Deals and find highlights in our Prime Day liveblog. Photograph: Simon Hill Baseus Mini Retractable USB-C Cable $17 $11 (35% off) Amazon Baseus' retractable USB-C cable avoids tangles with preset lengths (1.1-3.3 ft) and auto-rewinds into its case. Photograph: Amazon Valtech Magna-Tiles $50 $35 (30% off) Amazon Magna-Tiles—beloved STEM toys—let kids build 2D/3D creations with magnetic shapes. Photograph: Simon Hill Ravensburger Labyrinth $30 Amazon Labyrinth is a top family game that has kids collect treasures by shifting maze tiles each turn.