Enter in R-mode or direct G-mode, and perform a Crystal Flash in the morph nook to the top-left of Mother Brain. During the Crystal Flash, allow the Rinkas to damage Samus down and trigger an auto-reserve refill, which will interrupt the Crystal Flash.

The interruption of the Crystal Flash (due to the R-mode forced standup) limits the damage that Samus takes during it; After the reserve trigger, Samus will take just one more Rinka hit.

Entrance condition:

{
  "comeInWithGMode": {
    "mode": "direct",
    "morphed": true
  }
}

Requires:

{
  "notable": "Moondance Clip"
}
{
  "not": "f_MotherBrainGlassBroken"
}
"h_canArtificialMorphMovement"
"h_canArtificialMorphCrystalFlash"
{
  "resourceMaxCapacity": [
    {
      "type": "RegularEnergy",
      "count": 299
    }
  ]
}
{
  "autoReserveTrigger": {
    "minReserveEnergy": 100
  }
}
{
  "enemyDamage": {
    "enemy": "Rinka",
    "type": "contact",
    "hits": 1
  }
}
{
  "gainFlashSuit": {}
}

Dev note: Having a small amount of E-Tanks ensures the reserve tanks can be filled by the Crystal Flash before the auto-reserve trigger. FIXME: A larger amount of E-Tanks can also work, but the reserves will not completely fill, so less energy would remain at the end.