Elite cages with elite bottle - don’t think I’ve had a drop since I went that way. I generally use elite fly bottles.
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Tacx Ciro cages on both my bikes, regardless of bottles used, a lot of the WT teams use them also.
Cheap, light, lots of colour options, durable. Did a 108km MTB race last weekend on my gravel bike(!), zero bottle issues 
Elite Custom Race (plastic) and I almost always use Camelbak Podium bottles.
I did have a 500ml Fly bottle, but it’s the only bottle I’ve ever lost on a ride (on a rather spirited gravel descent, but still)
I see that Elite have updated the Fly bottles to have more texture - maybe because they can slip out? The bottle I have was very flexible, and it wasn’t full when it disappeared forever.