The ground-based characterization of asteroids is a key step for planning their exploration. The near-Earth asteroid 155140 (2005 UD) is a potential flyby target of Japan Aerospace Exploration Agency's DESTINY+ (Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science) mission, while (612267) 2001 SG286 has been considered as a possible target for in-situ exploration. We aim to determine their physical properties using the observations obtained with various telescopes from Canary Islands Observatory. For 2005 UD, we confirmed the two peak light curve, a rotation period of 5.224 $\pm$ 0.003 h and an amplitude of 0.34 mag. However, a three peak solution seemed also to fit the light curve, but this was discarded as implausible. Using the obtained visible to near-infrared spectrum we classified it as a Cb type, and we found a spectral matching with heated carbonaceous chondrite meteorites of CM2 type. The thermal emission flux at 2.2 $\mu \mathrm{ m}$ points to an albedo of $p_V = 0.06~\pm ~0.02$. There are significant differences in the spectrum of 2005 UD compared to that of (3200) Phaeton, hypothesized as its parent body. The accurate visible spectrum obtained with the Gran Telescopio Canarias indicate that 2001 SG286 is an S-type asteroid. The photometric data obtained with Isaac Newton Telescope suggest a rotation period of 12.30 $\pm$ 0.01 h and an amplitude of 0.64 mag. With these observations we found its absolute magnitude $H$ = 21.4 $\pm$ 0.3, and estimate its size as 160 $\pm$ 45 m.